Many of the current supercomputers tend to pursue higher peak performance, however, the characteristics of scientific applications are getting diversified, and their sustained performance strongly depends on not only the peak floating point operation performance of the system, but also its memory bandwidth. NEC’s goal is to provide superior sustained performance, especially for memory-intensive scientific applications. As the successor to the SX-9, its brand-new SX-ACE vector supercomputer has been developed to achieve this goal. The new vector processor features the world top-class single core performance of 64Gflop/s with the largest memory bandwidth of 64GB/s per core. Four cores, memory controllers, and a network controller are integrated into the SX-ACE processor, enabling the processor performance of 256Gflop/s with its memory bandwidth of 256GB/s. In order to gain a higher sustained performance, the system is equipped with a specialized network interconnecting processors, as well as a sophisticated vectorization compiler and an operating system.